Combined hydrocracking and catalytic dewaxing process

ABSTRACT

A PROCESS FOR PRODUCING JET FUEL FROM A HYDROCARBON FEEDSTOCK BOILING SUBSTANTIALLY BELOW ABOUT 1000*F. COMPRISING SEPARATING THE FEEDSTOCK INTO A FIRST 500*F.600*F. FRACTION AND A 600*F.-1000*F. FRACTION CONTACTING THE 600*-1000*F. FRACTION WITH HYDROGEN AND A HYDROCRACKING CATALYST IN A HYDROCRACKING ZONE AT HYDROCRACKING CONDITIONS; SEPARATING THE HYDROCRACKATE INTO A 100*F.-300*F. FRACTION, A 300*F.-500*F. FRACTION, AND A SECOND 500*F.-600*F. FRACTION; CONTACTING THE   500*F.-600*F. FRACTIONS WITH HYDROGEN AND A CATALYST COMPRISING MORDENITE IN HYDROGEN FORM AND AT LEAST ONE HYDROGENATING COMPONENT IN A CATALYTIC DEWAXING ZONE AT CATALYTIC DEWAXING CONDITIONS; AND SEPARATING THE CATALYTIC DEWAXATE INTO A SECOND 100*F.-300*F. FRACTION AND A 300*F.-600*F. JET FUEL. THE HYDROCARBON FEEDSTOCK IS PREFERABLY A HYDROFINED HYDROCARBON FEEDSTOCK.

C. J. EGAN Aug. 1, 1972 COMBINED HYDROCRACKING AND CATALYTIC DEWAXINGPROCESS 3 Sheets-Sheet 3 Filed Nov. 27, 1970 huh 508 03 fi omm kow mooop wJU Umm I mJU Umm I m oooToow INVENTOR CLARK J. EGAN BY W2 5, n I 7AT ORNEYS .iiwll m oow oom U .rmh

m oom Oom A m ooe xookwommm zomm ooma z 3210mm:

United States Patent US. Cl. 20880 12 Claims ABSTRACT OF THE DISCLOSUREA process for producing jet fuel from a hydrocarbon feedstock boilingsubstantially below about 1000 F. comprising separating the feedstockinto a first 500 F.- 600 F. fraction and a 600 F.-1000 F. fraction;contacting the 600-1000 F. fraction with hydrogen and a hydrocrackingcatalyst in a hydrocracking zone at hydrocracking conditions; separatingthe hydrocrackate into a 100 F.-300 fraction, a 300 F.500 P. fraction,and a second 500 F.600 F. fraction; contacting the 500 F.-600 F.fractions with hydrogen and a catalyst comprising mordenite in hydrogenform and at least one hydrogenating component in a catalytic dewaxingzone at catalytic dewaxing conditions; and separating the catalyticdewaxate into a second 100 F.-300 F. fraction and a 300 F.600 F. jetfuel. The hydrocarbon feedstock is preferably a hydrofined hydrocarbonfeedstock.

BACKGROUND OF THE INVENTION This invention is concerned with producinglow freeze point jet fuel in high yield from hydrocarbon feedstocksboiling above about 500 -F.

The world demand for jet fuel has been increasing steadily. Thisincreased demand can be expected to continue and probably evenaccelerate in the future. Maximization of the yield of jet fuel from ahydrocarbon feedstock is accordingly becoming economically moreattractive. This specification discloses and claims a novel combinedhydrocracking and catalytic dewaxing process which provides low freezepoint jet fuel in significantly increased yield.

SUMMARY OF THE INVENTION A process has now been discovered which permitsthe production of exceptionally high yields of low freeze point jetfuel. The process comprises separating a hydrofined hydrocarbonfeedstock boiling below about 1000 F., and preferably obtained byhydrofining a hydrocarbon feedstock boiling within the range from about500 -F. to about 1000 E, into a first 500 F.-600 F. fraction, and a 600F.1000 P. fraction. The 600 F.-1000 F. fraction is then conducted to ahydrocracking zone where it is contacted with hydrogen and ahydrocracking catalyst at hydrocracking conditions. The hydrocrackatefrom the hydrocracking zone is then separated in a separation zone intoa. 100 F.300 F. fraction, a 300 F.500 F. fraction and a second 500F.-600 F. fraction. The separation of the hydrocrackate may, if desired,be performed in the same separation zone as is the separation of thehydrofined hydrocarbon feedstock boiling below about 1000 -F. In thiscase, instead of their being a first 5 00 F 600 F. fraction and a second500 F.600 F. fraction, there will be only a single 500 F.-600 F.fraction. The first and second 500 F.-600 F. fractions or the single 500F.-600 F. fraction if a single separation zone is used as discussedabove, are contacted with hydrogen and a catalyst comprising mordenitein hydrogen form and a hydrogenation component in a catalytic dewaxingzone at catalytic dewaxing conditions. The catalytic dewaxate from thecatalytic dewaxing zone is then separated into a F".300 F. fraction anda 300 F.600 -F. jet fuel. Since jet fuel specifications generallyrequire the jet fuel to boil Within a 300 F .5 50 F. range, it Willusually be desirable to separate the catalytic dewaxate into a 100 F.300 P. fraction, a 300 F.550 F. jet fuel, and a 550 F.-600 F. fraction.The 550 F.600 F. fraction may then desirably be recycled to thehydrocracking zone.

The necessity for jet fuels to be characterized by low freeze points iswell known, and is reflected in all military and commercial jet fuelspecifications. Many patents have been issued directed to variousprocesses for producing low freeze point jet fuels, for example, US.Pat. 3,110,- 662. Said patent also indicates that it is known tohydrocrack hydrocarbon feedstocks containing materials boiling above thejet fuel boiling range, to produce jet fuels.

Catalytic dewaxing of hydrocarbon oils is well known in the art andrefers to the reduction of the normal paratfin content of the oils bycatalytic conversion of normal parafiins rather than by mere physicalremoval of normal parafiins without conversion thereof.

US. Patent 3,539,495 to Egan, adequately discusses the reasons forcatalytic dewaxing of hydrocarbon oils, including reasons why continuingefforts are being made in the petroleum industry to find improveddewaxing catalysts and processes.

A recent development in the area of catalytic dewaxing is provided byaccomplishing catalytic dewaxing with a catalyst comprising acrystalline aluminosilicate zeolite in hydrogen form having uniform poreopenings with a minor pore diameter as determined by crystallography ofnot less than 5.8 and a major pore diameter less than 8 angstroms at atemperature of at least 450 F., as disclosed in Texaco DevelopmentCorporation South Africa Pat. 67 3,685. The zeolite having the requiredcharacteristics is a mordenite-type zeolite.' It is highly preferablethat the mordenite be in hydrogen form; the sodium form, for example,produces inferior dewaxing results. A catalytic material, suitably aGroup VIII metal, preferably a. platinum group metal, preferably isassociated with the zeolite. The decationized mordenite-type zeolitestructures have pore sizes sufficiently large to admit not only thestraight-chain hydrocarbons which it is desired to selectively convertto lower molecular weight materials, but also cyclic hydrocarbons; incontrast, the straight-chain hydrocarbons alone are selectively admittedto S-angstrom molecular sieves, the pores of which quickly becomesaturated with waxy components, causing catalyst deactivation.Accordingly, the decationized mordenite zeolite structures have agreater capacity for sustained selective conversion of straight-chaincomponents than do S-angstrom molecular sieves. The mordenite-typezeolite has a chaintype zeolite structure in which a number of chainsare linked together into a structural pattern with parallel sorptionchannels similar to a bundle of parallel tubes, in contrast with thethree-dimensional structural lattices which are characteristic ofmolecular sieve zeolites such as Y-type faujasites. The mordenite-typezeolite dewaxing catalyst preferably comprises a Group VIIIhydrogenating component, particularly nickel, platinum, palladium andrhodium, in an amount of 0.1 to 10 weight percent, calculated as metal.When the hydrogenating component is platinum or palladium, therecommended amount is 0.1 to 5.0 weight percent, preferably 0.5 to 2.5weight percent. When the hydrogenating component is nickel, cobalt oriron, the recommended amount is 1 to 10 weight percent, preferably 1 to5 weight percent. Hydrogen, in conjunction with the hydrogenatingcomponent of the catalyst, extends the life of the catalyst duringcatalytic dewaxing by preventing fouling of the pore openings of thecatalyst. The catalyst may be preconditioned in hydrogen before use, ata temperature in the range of 450 to 1000 F.

A mordenite-type zeolite in hydrogen form that is suitable for purposesof the process of said South Africa Pat. 67/ 3,685 and for purposes ofthe present invention is the calcined synthetic Zeolon H mordenite soldcommercially by the Norton Company.

As used herein, the terms mordenite, hydrogen mordenite, and mordenitein hydrogen form are intended to include those mordenite-type zeolitesindicated by said South Africa Pat. 67/3,685 to be desirable ascatalytic dewaxing catalysts or as components of catalytic dewaxingcatalysts.

As used herein, the terms hydrocrackate and catalytic dewaxate mean theeflluents from the hydrocracking zone and catalytic dewaxing zone,respectively.

DRAWINGS The above and additional objects of the present invention, andthe ways in which these objects are achieved, will be better understoodfrom the following description when read in connection with theaccompanying drawings, which are a diagrammatic illustration ofapparatus and flow paths suitable for carrying out certain embodimentsof the invention.

DETAILED DESCRIPTION OF THE INVENTION Feedstock The hydrocarbonfeedstock boiling substantially below about 1000 F. contains at leastweight percent, preferably 5 to 40 Weight percent, and more preferablyat least Weight percent, and still more preferably 10 to 30 weightpercent, normal paraffins. Generally the hydrocarbon feedstock has afreeze point above 10 F. and more usually above about 0 F. Thehydrocarbon feedstock can, for example, be a hydrofined hydrocarbonfeedstock obtained by hydrofining a hydrocarbon feedstock boiling Withinthe range from about 500 F. to about 1000 F. using a conventionalhydrofining catalyst and conditions. Suitable hydrofining catalystsinclude, for example, cobalt and molybdenum or nickel and tungsten intheir oxide or sulfide forms, preferably supported on a porous solidcarrier, e.g., alumina, silica, titania and the like. Other oxides and/or sulfides of Group VI-B and/ or Group VIII metals may alternatively beincluded with the catalyst. Preferably the nitrogen content of thehydrofined hydrocarbon feedstock is below about 10 ppm. Preferably thesulfur content of the hydrofined hydrocarbon feedstock is below about 50p.p.m. The nitrogen and sulfur contents of the 500 F.-1000 F.hydrocarbon feedstock that is converted into the hydrofined hydrocarbonfeedstock are generally above about 10 p.p.m. and 50 p.p.m.respectively.

Hydrocracking conditions and catalysts The conditions in thehydrocracking zone preferably include a temperature Within the rangefrom 400 F. to

950 F., preferably 750 F. to 850 F a pressure within the range from 500p.s.i.g. to 3500 p.s.i.g., preferably 1000 p.s.i.g. to 2500 p.s.i.g., aliquid hourly space velocity within the range from 0.1 to 10 volumes of600 F.+ hydrocracker feedstock per volume of catalyst per hour, and atotal hydrogen rate of 200 s.c.f. to 20,000 s.c.f., preferably 2000s.c.f. to 8000 s.c.f. of hydrogen per barrel of said feedstock, and aper-pass cracking conversion of the 600 F.l000 F. hydrocracker feedstockof more than 30 weight percent, preferably 40 to 80 weight percent.

The nature of the hydrocracking catalyst used for hydrocracking the 600F.-1000 F. hydrocracker feedstock is not critical, i.e., any of the manyprior art hydrocracking catalysts may be used. For example, a catalystcomprising a nickel component and a tin component associated with aporous acidic inorganic oxide carrier as described in US. Pat.3,399,132, issued Aug. 27, 1968 to B. F. Mulaskey, ahydrocracking-isomerization catalyst comprising a crystalline zeoliticmolecular sieve component, a silica-containing gel component, a Group VIhydrogenating component, and a Group VIII hydrogenating component, acatalyst comprising a layered crystalline aluminosilicate clay-typemineral as described in detail in US. Pat. 3,252,757, which hasassociated therewith a palladium component and an additional metalcomponent, for example, a member of Group VI, Group VIII, the LanthanideSeries, the Actinide Series, rhenium, or the like. Other hydrocrackingcatalysts are usable as well. The preferred hydrocracking catalystcomprises a nickel component and a tin component associated with aporous acidic inorganic oxide carrier as described in the aforementionedU.S. Pat. 3,399,132.

Separating the feedstocks.

It is important that the feedstocks be separated into the fractionsindicated above. Well known separation techniques, for example,distillation, will serve to accomplish this.

When a temperature is specified to define a feed or a product, it is tobe understood that the temperature is approximate and may be changed toa temperature within about :35 F., but more preferably within about :15F. of the specified temperature without departing from the teachings ofthe invention disclosed herein.

Catalytic dewaxing conditions and catalyst The catalytic dewaxingconditions preferably include a temperature within the range from 400 F.to 900 F., preferably 500 F. to 750 F., a pressure within the range fromp.s.i.g. to 2500 p.s.i.g., preferably 400 p.s.i.g. to 2000 p.s.i.g., aliquid hourly space velocity within the range from 0.2 to 25 volumes of500 F.-600 F. catalytic dewaxer feedstock per volume of catalyst perhour, and a total hydrogen rate of 200 s.c.f. to 20,000 s.c.f.,preferably 2000 s.c.f. to 8000 s.c.f. of hydrogen per barrel of thecatalytic dewaxer feedstock.

The dewaxing catalyst must comprise mordenite in hydrogen form and atleast one hydrogenating component, for example, a Group VIIIhydrogenating component, preferably selected from the group consistingof platinum, palladium, iridium, ruthenium, rhodium, and nickel, andcompounds of these metals more preferably palladium. The dewaxingcatalyst advantageously further may comprise carbon in an amount of atleast 0.5 weight percent based on the total catalyst. The carbon contentof the catalyst may be obtained by contacting the catalyst with hydrogenand a heavy hydrocarbon distillate boiling within the range from 500 F.to 1100 F. at a temperature within the range from 400 F. to 900 F., apressure within the range from 500 p.s.i.g. to 3500 p.s.i.g., and aliquid hourly space velocity within the range from 0.1 to 10, at a totalhydrogen rate in the range from 200 s.c.f. to 20,000 s.c.f. of hydrogenper barrel of said distillate until the catalyst contains the desiredamount of carbon. It has been found that the presence of the carbon inthe catalyst makes the catalyst more selective for cracking normalparaffins, and therefore makes the catalyst a more efiicient dewaxingcatalyst. The amount of the hydrogenating component present in thedewaxing catalyst is discussed above.

The dewaxing catalyst in the catalytic dewaxing zone advantageously maycontain a rhenium component, i.e., rhenium or a compound of rhenium, inan amount from 0.2 to 1.5 weight percent, calculated as the metal andbased on the total catalyst.

Preferably, the smoke point of the 500 F.600 F. fraction is increased bycontacting it with a smoke point elevation (hydrogenation) catalyst,comprising for example, a Group VIII noble metal component associatedwith a porous inorganic oxide, e.g., alumina, silica, or magnesiacatalyst, in a smoke point elevation (hydrogenation) zone either beforeor after it is contacted with the catalyst comprising mordenite inhydrogen form and a hydrogenation component. Preferably, the porousinorganic oxide is alumina. The smoke point elevation conditions shouldinclude a temperature in the range from 350 F.700 F., and preferablyfrom 550 F.-6 50 F. The upper temperature limit (700 F.) is chosen so asto avoid significant hydrocracking. The lower limit of the temperature(350 F.) is chosen so as to assure significant smoke point elevationactivity. The smoke point elevation conditions further include apressure within the range from about 300 p.s.i.g. to about 3000p.s.i.g., preferably 400 p.s.i.g. to 2000 p.s.i.g., a liquid hourlyspace velocity within the range from about 0.1 to about 10 volumes of500 F.-600 F. catalytic dewaxer feedstock (or catalytic dewaxate) pervolume of catalyst per hour, and a total hydrogen rate of 200 s.c.f. to20,000 s.c.f., preferably 2000 s.c.f. to 8000 s.c.f. of hydrogen perbarrel of the catalytic dewaxer feedstock (or catalytic dewaxate). Inthe smoke point elevation zone, aromatic (and olefinic) hydrocarbon arehydrogenated to form saturated hydrocarbons.

DETAILED DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood by reference to the specific embodiments thereof illustratedin FIGS. 1-4. The embodiment illustrated in FIG. 1 may be described asfollows.

A hydrocarbon feedstock boiling within the range from about 500 F. toabout 1000 F. is introduced via line 1 into hydrofiner 2. Hydrogen isintroduced into hydrofiner 2 via line 3. Recycle hydrogen is also addedto hydrofiner 2 via line 6. Hydrofiner 2 may contain any conventionalhydrofining catalyst. Hydrofined hydrocarbon feedstock and hydrogenleave hydrofiner 2 via line 4 and enter vapor-liquid separator 5 whereinhydrogen and sulfur and nitrogen impurities are separated from thehydrofined hydrocarbon feedstock which is conducted via line 7 toseparator 8. Gas boiling below about 100 F. is separated from thehydrofined hydrocarbon feedstock in separator 8. A first naphthafraction boiling within the range from about 100 F. to about 300 F. isrecovered from separator 8 via line 9. A 300 F.-500 F. jet fraction isrecovered from separator 8 via line 10.

A 500 F.600 F. catalytic dewaxer feedstock is conducted from separator 8via line 11 to catalytic dewaxer 12. Hydrogen is introduced intocatalytic dewaxer 12 via line 13. The catalytic dewaxate and hydrogenare conducted from catalytic dewaxer 12 to vapor-liquid separator 15 vialine 14. Recycle hydrogen is conducted from vapor-liquid separator 15into catalytic dewaxer 12 via line 16. The catalytic dewaxate isconducted from vaporliquid separator 15 via line 17 to separator 18. Gasboiling below about 100 F. is separated from the catalytic dewaxate inseparator 18. A 100 F.300 F. third naphtha fraction is recovered fromseparator 18 via line 19. A 300 F.-600 F. jet fuel fraction is recoveredfrom separator 18 via line 20.

A 600 F.-1000 F. fraction is conducted from separator 8 via line 21 tohydrocracker -22. Hydrogen is conducted to hydrocracker 22 via line 23.The hydrocrackate and hydrogen are conducted from hydrocracker 22 tovapor-liquid separator 25 via line 24. Recycle hydrogen is conductedfrom vapor-liquid separator 25 to hydrocracker 22 via line 26. Thehydrocrackate is conducted from vapor-liquid separator 25 via line 27 toseparator 28. Gas boiling below about 100 F. is separated from thehydrocrackate in separator 28. A second 100 F.- 300 F. naphtha fractionis recovered from separator 28 via line 29. A second 300 F.-500 F. jetfuel fraction is recovered from separator 28 via line 30. A second 500F.-600 F. catalytic dewaxer feedstock is conducted from 6 separator 28via line 31 to catalytic dewaxer 12., A 600 F.-1000 F. recycle fractionis conducted from separator 28 via line 32 to hydrocracker 22.

As indicated in FIG. 2, it is possible and often advantageous to conductthe hydrocrackate boiling below about 1000 F. from vapor-liquidseparator 25 via line 27 to separator 8. This eliminates the necessityfor separator 28. As also indicated in FIG. 2, it is possible and oftenadvantageous to separate the catalytic dewaxate in separator 18 into a100 F.-300 F. third naphtha fraction (line 19), a 300 F.-550 F. jet fuel(line 20), and a 500 F.-600 F. recycle fraction which is conducted vialine 40 to hydrocracker 22.

As indicated in FIG. 3, it is possible and often advantageous to subjectthe 500 F.-600 F. catalytic dewaxer feedstock to smoke point elevation.This can be accomplished, as is diagrammatically indicated, by includinga smoke point elevator 32 in line 11 or line 17. In the smoke pointelevator 32, hydrogen is introduced via line 3 3 and hydrogen recycle isintroduced via line 36. In a smoke point elevation zone the 500 F.-600F. catalytic dewaxer feedstock (or the catalytic dewaxate) and hydrogenare contacted with a smoke point elevation catalyst. The efiluent fromthe smoke point elevator 32 may be passed via line 34 to a vapor-liquidseparator 35 wherein hydrogen is removed for recycle via line 36 andcondensable gases and liquid are moved via lines 11 or 17.

Alternatively, it is not necessary to separate hydrogen from the smokepoint elevation zone efiluent. Thus, as illustrated in FIG. 4, forexample, the smoke point elevation and catalytic dewaxing zones can beincorporated within a single reactor. This can be done by packing thetop of the reactor with a smoke point elevation catalyst and the bottomof the reactor with a catalyst comprising mordenite in hydrogen form andat least one hydrogenating component, or vice versa.

Conventional heating means are, of course, included where necessary toprovide reactants and/or reaction zones at desired temperatures. Theheating means are not illustrated since they constitute a well-knownpart of the prior art and their inclusion would only serve to make thedrawings more difiicult to comprehend.

The naphtha fractions obtained may, of course, be combined to form asingle naphtha blending stock. Similarly, the jet fuel fractionsproduced may be combined to form a single jet fuel to exceptionally lowfreeze point and having a smoke point above about 18 mm.

The reaction conditions and catalysts within the smoke point elevation,hydrofining, and hydrocracking zones are as previously identified.

The invention will be better understood by reference to the illustrativeexample which follows.

EXAMPLE In each of two experiments, a 500 F.-600 F. fraction from ahydrocracker said 500 F.-600 F. fraction having a freeze point of 7 F.and hydrogen were contacted in a single reactor, first with a bed ofcatalyst comprising 0.39 weight percent platinum, 0.35 weight percentrhenium, 0.46 weight percent fluorine and 0.18 weight percent chlorineassociated with alumina and then with a catalyst bed where the catalystcomprised 1.7 weight percent palladium and mordenite in hydrogen form.In the first of the two experiments, the temperature of thealumina-based (smoke point elevation) catalyst reaction zone wasmaintained at 210 F. and the temperature of the mordenite (catalyticdewaxer) reaction zone was maintained at 632 F. In the secondexperiment, the respective temperatures were maintained at 550 F. and615 F. As discussed earlier in the specification, the aluminabasedcatalyst does not cause smoke point elevation when contacted with thefraction at 210 F. (below 350 F.)

is maintained at a temperature of 550 F. Table 1 below shows thereaction conditions used and the yields of product obtained in theabove-described experiments.

TABLE 1 Smoke point elevation zone at- 210 F: and 550 F. and catalyticcatalytic dcwaxing zone dewaxing zone at 632 F. at 615 F.

Reaction conditions:

LHSV (smoke point elevation The data in the table show that a low freezepoint product is obtained by the method of the invention using bothreaction conditions wherein smoke point elevation is obtained andconditions wherein smoke point elevation is not obtained. The data inthe table further show that the smoke point of the 300 F.+ product iswell above 20 mm. when the smoke point elevation zone is maintained at atemperature wherein effective smoke point elevation occurs.

The process of the present invention leads to the production of a jetfuel having a freeze point below about F. and preferably below about 20F. The freeze point of the jet fuel produced is lower than the freezepoint of the hydrofined hydrocarbon feedstock by at least F., moreusually, by at least F., and still more usually, by at least 30 F. Thesmoke point of the jet fuel, when a smoke point elevation step is notincluded with the process of the invention, is generally about 18 mm. orhigher. When a smoke point elevation step is included, the smoke pointof the jet fuel is generally about 20 mm. or higher. While the inventionhas been described in connection with specific embodiments thereof, itwill be understood that it is capable of further modification, and thisapplication is intended to cover any variations, uses, or adaptations ofthe invention following, in general, the principles of the invention andincluding such departures from the present disclosure as come withinknown or customary practice in the art to which the invention pertainsand as may be applied to the essential features hereinbefore set forth,and as fall within the scope of the invention and the limits of theappended claims.

The invention is hereby claimed as follows:

1. A process for producing jet fuel from a hydrocarbon feedstock boilingsubstantially below about 1000 F., the jet fuel having a freeze pointbelow about 0 F. comprising:

(1) separating the hydrocarbon feedstock into a first 500 F.-600 F.fraction and a 600 F.1000 F. fraction;

(2) contacting the 600 F.1000 F. fraction with hydrogen and ahydrocracking catalyst in a hydrocracking zone at hydrocrackingconditions;

(3) separating the hydrocrackate into a first 100 F.- 300 F. fraction, a300 F.500 F. jet fraction, and a second 500 F.600 F. fraction;

(4) contacting the first 500 F.600 F. fraction, the second 500 F.600 F.fraction and hydrogen with a catalyst comprising mordenite in hydrogenform and at least one hydrogenation component in a catalytiic dewaxingzone at catalytic dewaxing conditions; an

8 (5) separating the catalytic dewaxate into a second F.-300 F. fractionand a 300 F.600 F. jet fuel.

2. A process as in claim 1, wherein a single separation zone is used toseparate the hydrocarbon feedstock and the hydrocrackate, and the firstand second 500 F.600 F. fractions are separated together as a single 500F.- 600 F. fraction.

3. A process as in claim 1, including, as an added step:

combining the first 100 F.-300 F. fraction and the second 100 F.-300 F.fraction.

4. A process as in claim 1, including, as an added step:

combining the 300 F.500 F. jet fraction and the 300 F.600 F. jet fuel.

5. A process as in claim 1, wherein the hydrocracking catalyst comprisessilica-alumina, nickel, and tin.

6. A process as in claim 1, including providing the hydrocarbonfeedstock by the step comprising:

contacting a hydrocarbon feedstock having above about 10 p.p.m. nitrogenand above about 50 p.p.m. sulfur and boiling within the range from about500 F. to about 1000 F. with hydrogen and a hydrofining catalyst in ahydrofining zone at hydrofining conditions. 7. A process as in claim 1,including as an added step: contacting the first and second 500 F.600 F.fractions with hydrogen and a smoke point elevation catalyst in a smokepoint elevation zone at smoke point elevation conditions, including atemperature from 350 F. to 700 F.

8. A process as in claim 1, including as an added step:

contacting the catalytic dewaxate with hydrogen and a smoke pointelevation catalyst in a smoke point elevation zone at smoke pointelevation conditions, including a temperature from 350 F. to 700 F.

9. A process as in claim 1, wherein the catalytic dewaxing conditionsfall within about the following ranges:

temperature, 400 F. to 900 F.;

pressure, 100 p.s.i.g. to 2500 p.s.i.g.;

liquid hourly space velocity, 0.2 to 25; and

total hydrogen rate, 200 s.c.f. to 20,000 s.c.f. hydrogen per barrel ofthe first and second 500 F.600 F. fractions.

10. A process as in claim 1, wherein the hydrocracking conditions fallwithin about the following ranges:

temperature, 400 F. to 950 F.;

pressure, 500 p.s.i.g. to 3500 p.s.i.g.;

liquid hourly space velocity, 0.1 to 10; and

total hydrogen rate, 200 s.c.f. to 20,000 s.c.f. hydrogen per barrel ofthe 600 F.1000 P. fraction.

11. A process as in claim 1, including, as added steps:

separating the 300 F.600 F. jet fuel into a 300 F.-

550 F. jet fuel and a 550-600 F. recycle fraction; and

conducting the 550 F'-600 F. recycle fraction to the hydrocracking zone.12. A process for producing jet fuel having a freeze point below about 0F. and a smoke point above about 18 mm., comprising:

separating a hydrofined hydrocarbon feedstock boiling below about 1000F. into a first naphtha fraction boiling within the range from about 100F. to about 300 F., a first jet fuel fraction boiling within the rangefrom about 300 F. to about 500 F., a first dewaxer feedstock boilingwithin the range from about 500 F. to about 600 F., and a hydrocrackerfeedstock boiling from about 600 F. to 1000 F.;

conducting the hydrocracker feedstock to a hydrocrackmg zone;

contacting the hydrocracker feedstock with hydrogen and a hydrocrackingcatalyst in the hydrocracking zone at hydrocracking conditions;

conducting a hydrocrackate from the hydrocracking zone to a separationzone;

separating in the separation zone a second naphtha frac tion boilingwithin the range from about 100 F. to

about 300 F., a second jet fuel fraction boiling within the range fromabout 300 F. to about 500 F., and a second dewaxer feedstock boilingwithin the range from about 500 F. to about 600 F.;

conducting the first dewaxer feedstock and the second dewaxer feedstockto a catalytic dewaxing zone;

contacting the first dewaxer feedstock, the second dewaxer feedstock,and hydrogen with a catalyst comprising mordenite in the hydrogen formand a hydrogenation component in the catalytic dewaxing zone atcatalytic dewaxing conditions;

conducting a catalytic dewaxate from the catalytic dewaxing zone to aseparating zone; and

separating the catalytic dewaxate into a third naphtha fraction boilingfrom about 100 F. to about 300 F. and a jet fuel boiling within therange from about 300 F. to about 600 F.

References Cited UNITED STATES PATENTS 11/ 1963 Scott et a1. 208883/1966 Mason et a1. 20859 8/1966 Gould 20878 12/ 1967 Peck et a1 208598/ 1968 Mulaskey 2081 11 4/ 1970 Haney 20860 12/1970 Jacobs et a1. .320859 11/1970 Egan 20859 11/1970 Morris et al 208-1 11 DELBERT E. GANTZ,Primary Examiner 5 G. E. SCHMITKONS, Assistant Examiner US. Cl. X.R.

